This invention relates generally to the field of interchangeable cooking cartridges for use in a free-standing or built-in cooking appliance. The invention relates more particularly to an airflow system for cooling the internal components of a cooking cartridge.
In the field of magnetic induction cooking an induction coil is located below the cooktop surface and is used to generate an oscillating circular magnetic field. When an iron-based cooking utensil is placed in the magnetic field, it acts as a shorted transformer secondary which is subject to a high induction current at low voltage. The cooking utensil is heated directly without heating the cooktop surface first and the heat from the cooking utensil cooks the food, not the induction field, since heat is generated in the utensil which itself becomes the burner.
Because of the heat generated by the induction coil and the electronic circuitry for operating the induction coil, which are both located below the cooking surface within the cooking cartridge, it is necessary to provide some form of cooling for the induction coil and its associated circuitry.
Prior art has shown electric fans operable for moving a cooling airflow over the various components which are to be cooled. U.S. Pat. No. 4,191,875 issued to Cunningham on Mar. 4, 1980, is specifically directed toward controlling operation of an internal electric fan for cooling induction heating apparatus. A thermistor is located near the induction heating apparatus and controls operation of the fan. The thermistor, in the preferred embodiment, is in series with a variable resistor and a capacitor. When the capacitor is charged to a predetermined voltage through the thermistor and variable resistor it will fire an SCR through a diac to allow current to flow through the SCR and operate the fan motor. Cunningham shows a plurality of air inlet and outlet holes in the walls of the housing so that the fan randomly pulls air in one side and exhausts out the other side of the housing after passing over the induction heating apparatus.
U.S. Pat. No. 4,415,788 issued to Field on Nov. 15, 1983, teaches an induction cartridge having a forced air cooling system where a fan draws air into the cartridge cavity, circulates it around the induction heating components and exhausts it out an opening in the bottom of the cartridge. The patent discloses exhausted air being returned to the kitchen environment through an exhaust gap around the periphery of the cartridge between the housing top and the bottom of a support flange.
The prior art has thus recognized the need for cooling induction heating components and has shown particular circuitry utilizng a thermistor for controlling operation of an air moving fan responsive to the temperatures generated within a housing containing these components. There has also been shown a particular airflow path whereby an internal fan draws cooling air directly into a cooking cartridge, across the induction heating components, out an opening in the bottom of the cartridge and exhausts the heated air above the range surface through a gap all around the cartridge between a support flange the range surface. There has been no known showing, however, of a modular cooking cartridge where the internal fan draws cooling air into the interior of the cooking cartridge through the cartridge top, over the induction heating components and out through exhaust openings in the cartridge top by way of an airflow path including an opening in the cooking cartridge container and an exhaust conduit formed by the cartridge container and an axuiliary housing fixed to the container.